1. Field of the Invention
The present invention relates to a solid state imaging device provided with a transparent component such as glass bonded to a light receiving surface and a method for manufacturing the same.
2. Description of Related Art
A known solid state imaging device using a CCD (charge coupled device) is provided with a solid state imaging element including a photodiode as a light receiving element and a microlens provided above it and a transparent component such as glass for protecting the solid state imaging element.
FIGS. 6A and 6B are sectional views illustrating the structure of a conventional solid state imaging device. In the conventional solid state imaging device, as shown in FIG. 6A, recesses are formed in the top surface of a substrate 101 for forming CCD solid state imaging elements on a subpixel-by-subpixel basis and photodiodes 102 for converting incident light 111 into an electronic signal are provided at the bottom of the recesses, respectively. A first acrylic planarization film 103 is formed on the substrate 101 to make the uneven top surface of the substrate flat. Color filters 104 are formed on the first acrylic planarization film 103 in one-to-one relationship with the photodiodes 102. A second acrylic planarization film 105 is formed on the color filters 104 to bury the unevenness caused by the color filters 104 and the gaps therebetween. Further, microlenses 106 are formed on the second acrylic planarization film 105 in one-to-one relationship with the photodiodes 102.
As shown in FIG. 6B, a solid state imaging element 113 including the photodiodes 102, color filters 104 and microlenses 106 formed on the substrate 101 is placed in a package 112 and the top of the package 112 is covered with a transparent component 109. An air layer (space) 110 exists in the package 112 between the solid state imaging element 113 and the back surface of the transparent component 109 as shown in FIGS. 6A and 6B. Referring to FIG. 6A, the light 111 passes through the transparent component 109 to enter the microlenses 106 and at the same time, reflection occurs on the top and back surfaces of the transparent component 109 and the top surfaces of the microlenses 106. In the conventional solid state imaging device, sufficient sensitivity has been obtained with the light transmitted to the photodiodes 102 only. However, according to finer design rules of the solid state imaging device adopted in recent years, it has been getting more difficult to obtain satisfactory sensitivity only with the light collected by the microlenses. As a solution to this, Japanese Patent No. 2719238 proposes a structure having an anti-reflection film formed on the microlenses.